This invention relates generally to pen cartridge devices adapted for use with industrial chart recorders, and more particularly to inexpensive, universally-applicable cartridges which are useable with various types of chart recorders and which are sufficiently low in cost that they can be disposed of after the intended period of use has expired.
Heretofore, various mounting arrangements have been proposed and produced, for enabling quick and easy demountable installation of a pen cartridge on the writing arm of a chart recorder. Usually such cartridges comprise an elongate hollow container which carries the ink, a stylus, and a means for attaching the container to the movable pen arm.
Some prior cartridges were provided with longitudinal grooves in the container body, adapted to receive the end portion of the pen arm. With these cartridges, close tolerances were necessary to enable the walls of the groove to properly frictionally grip and hold the side edges of the pen arm. Such tolerances had the disadvantage that the cost of the cartridge was undesirably increased, and also that slight variations in the widths of pen arms of different makes of recorders would defeat the purpose and negate the universality of the cartridge.
With other cartridge constructions, integral plastic lugs protruded from the surface of the cartridge body and were so spaced that the pen arm could be snapped or slipped into the spaces between, to secure assembly of the two parts. With this prior construction the lugs would sometimes break off, and also there existed the same disadvantage enumerated above for the grooved-type of cartridge body.
Moreover, in many cases the prior, replaceable pen cartridges were too difficult to install and remove. In consequence, bending or damage of the pen arm resulted, since such arms are usually constituted of a thin flat strip, usually of metal.